Topic 2 - bonding, structure and the properties of matter

• When does ionic bonding occur?

  When a metal combines with a non metal in a compound(oppositely charged ions)
• When does covalent bonding occur?

  Occurs between non metals sharing pairs of electrons
• When does metallic bonding occur?

  In metallic atoms and alloys

  -> atoms share delocalised electrons
• do metals become positively charged or negatively charged when they lose an electron?

  Positively charged
• do non-metals become positively charged or negatively charged when they gain an electron?

  Negatively charged
• Properties of ionic compounds

  • forms giant structures (giant ionic lattices)
  • every +ve ion is surrounded by a -ve ion (vice versa)
  • Strong forces of attraction between +ve and -ve ions (electrostatic forces of attraction)
  • Very high mpt + bpt because of the strong electrostatic forces
  • Can’t conduct electricity when they’re a solid but can when they’re melted or dissolved
• why do ionic compounds require a lot of energy?

  because of the strong electrostatic forces, energy is used to overcome / break them
• properties of small covalent bonds

  • low mpt + bpt -> usually gases or liquid at room temp
  • weak IMF between 2 molecules
  • doesnt requires a lot of energy
  • doesn’t conduct electricity
• what happens as a covalent molecule gets larger?

  IMF increases so their bpt would increase and require more energy
• Types of giant covalent molecules

  • Diamond
  • Silicone dioxide
  • Graphite / graphene
• diamond

  • formed from carbons
  • extremely hard substance
  • requires a lot of energy
  • can’t conduct electricity
• why can’t diamond conduct electricity?

  no free electrons to carry electrical charge
• silicone dioxide

  • contains silicone + oxygen covalently bonded together
  • high mpt + bpt = requires a lot of energy
• graphite

  • formed from carbon
  • soft + slippery
  • high mpt + bpt
  • good conductor of heat + electricity
  • arranged in layers but NO covalent bonds between the layers -> layers can slide over each other
  • 3 covalent bonds of carbon formed to 3 other carbon
• why is graphite a good conductor of heat + electricity?

  because it has delocalised electrons
• what are delocalised electrons?

  electrons which are free to move
• graphene

  • single layer of graphite
  • one atom thick
  • low density + really strong, high mpt + bpt
  • good conductor of electricity + heat
• What is fullerene?

  Molecules of carbon with hollow shape
• what was the first fullerene discovered called?

  buckminsterfullerene (6 or 5 rings of carbon atoms / hexagonal shaped - like a football)
• uses of fullerene ?

  drugs - pharmaceutical in the body

  lubricants - reducing friction in machines

  catalyst - speed up a chemical reaction
• carbon nanotubes (fullerene)

  • long cylinder
  • high tensile strength (can apply a high stretching force before it breaks)
  • delocalised electrons = good conductor of heat + electricity
• what are bonded in polymers?

  Monomers
• do polymers have a single or double covalent bond?

  Single
• what is an alloy?

  a mixture of metals

  • atoms are different sizes causing layers to be distorted
  • harder + stronger - needs a stronger force for the layers to slide over each other
• When does melting occur?

  occurs at the mpt - stronger force = more energy + higher mpt

  Solid -> liquid
• when does freezing occur?

  occurs below the mpt

  liquid -> solid
• when does boiling occur?

  occurs at the bpt

  liquid -> gas
• when does condensation occur?

  occurs at the same temp as bpt

  gas -> liquid